Adaptive filtering for canceling leaked transmit signal distortion from a received RF signal in an RF transceiver

ABSTRACT

Adaptive filtering is used to substantially cancel distortion in radio frequency (RF) signals. Such adaptive filtering can be used in an RF transmitting device to pre-compensate an RF signal with compensation (inverse) distortion to cancel inherent transmission path distortion from the RF signal. Adaptive filtering can also be used in a multi-carrier RF receiving device to cancel from a given carrier signal distortion due to cross talk from adjacent carrier signals. Adaptive filtering in an RF transceiver can be used to cancel from a received RF signal distortion arising from leakage of a transmit signal into the receive path.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is related to U.S. patent application Ser. No.13/533,012 entitled “Adaptive Filtering For Canceling Distortion InRadio Frequency Signals”, which is filed on the same day as the instantapplication.

BACKGROUND

Information (e.g., analog electrical signals, digital data, or the like)can be transmitted by modulating the information onto an RF carriersignal and then transmitting the modulated carrier signal from an RFtransmitter. An RF receiver can receive the transmitted modulatedcarrier signal and demodulate the carrier signal and thereby obtain theinformation. Various types of distortion can affect the transmitted andreceived signals. For example, linear and non-linear distortion can beintroduced in the transmitter and/or the transmitting antenna. Linearand non-linear distortion can also affect the transmitted signal as thesignal travels from the transmitter to the receiver. As another example,in a device for transmitting and/or receiving multiple RF carriersignals, each carrier signal can be distorted by cross talk fromadjacent carrier signals. As yet another example, in a transceiver(which is a device that both transmits and receives RF signals), asignal from the transmit path that is being prepared for transmissionfrom the transceiver can leak into a signal received at the transceiver.Embodiments of the present invention address these and other distortionin transmitted and/or received RF signals.

SUMMARY

In some embodiments, a radio frequency (RF) transceiver can include anRF transmitter configured to transmit RF signals and an RF receiverconfigured to receive incoming RF signals. The RF receiver can includean adaptive filter and a subtractor. The adaptive filter can beconfigured to filter, in accordance with a variable filteringcharacteristic, a distortion signal, which can correspond to atransmission path RF signal transmitted by the RF signal. The subtractorcan be configured to subtract from an RF signal received by the RFreceiver an output of the adaptive filter. The distortion signal can bea feedback signal from the RF transmitter or an output of a model of atransmission path of the RF transmitter.

In some embodiments, a process of canceling transmit signal leakagedistortion from a received RF signal in an RF transceiver that has an RFtransmitter and an RF receiver can include receiving an RF signal at theRF transceiver. The process can also include filtering with an adaptivefilter a distortion signal and subtracting an output of the adaptivefilter from the received RF signal. The distortion signal can be one ofa feedback signal from a transmission path of the RF transmitter or anoutput of a model of the transmission path of the RF transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of an RF transmitting module that usesadaptive filtering to pre-compensate an RF signal to cancel transmissionpath distortion from the RF signal according to some embodiments of theinvention.

FIG. 2 illustrates an example of a frequency pass-band of the RFtransmitting module of FIG. 1 and distortion inside and outside of thepass-band.

FIG. 3 illustrates an example of the RF transmitting module of FIG. 1 inwhich the control signal that controls the adaptive filter is providedby a model of the transmission path of the RF transmitting moduleaccording to some embodiments of the invention.

FIG. 4 illustrates an example of a configuration of the adaptive filterof FIG. 3 according to some embodiments of the invention.

FIG. 5 illustrates another example of the RF transmitting module of FIG.1 in which the control signal that controls the adaptive filter is afeedback signal from the transmission path of the RF transmitting moduleaccording to some embodiments of the invention.

FIG. 6 illustrates an example of a configuration of the adaptive filterof FIG. 5 according to some embodiments of the invention.

FIG. 7 illustrates an example of a multi-carrier RF receiving modulethat uses adaptive filtering to cancel from a given carrier signaldistortion due to cross talk from adjacent carrier signals according tosome embodiments of the invention.

FIG. 8 illustrates examples of frequency pass-bands of carrier signalsand in-band distortion according to some embodiments of the invention.

FIG. 9 shows an example of the multi-carrier RF receiving module of FIG.7 configured for three carrier signals according to some embodiments ofthe invention.

FIG. 10 illustrates an example of an RF transceiver that uses adaptivefiltering to cancel from a received RF signal distortion arising fromleakage of a transmit signal into the receive path according to someembodiments of the invention.

FIG. 11 shows examples of frequency pass-bands of the transmitter andreceiver of the RF transceiver of FIG. 10 with an example of distortiondue to leakage of a transmit signal into the receive path.

FIG. 12 illustrates an example of the RF transceiver of FIG. 10 in whichthe approximated distortion signal for controlling the adaptive filterof FIG. 10 is provided by a model of the transmission path of thetransmitter of the RF transceiver according to some embodiments of theinvention.

FIG. 13 illustrates an example of the RF transceiver of FIG. 10 in whichthe approximated distortion signal for controlling the adaptive filterof FIG. 10 is provided by a feedback from the transmission path of thetransmitter of the RF transceiver according to some embodiments of theinvention.

FIG. 14 shows an example of an RF transceiver in which adaptivefiltering is utilized to pre-compensate an RF signal to canceltransmission path distortion from the RF signal, cancel from a givencarrier signal distortion due to cross talk from adjacent carriersignals, and cancel from a received RF signal distortion arising fromleakage of a transmit signal into the receive path according to someembodiments of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

This specification describes exemplary embodiments and applications ofthe invention. The invention, however, is not limited to these exemplaryembodiments and applications or to the manner in which the exemplaryembodiments and applications operate or are described herein. Moreover,the Figures may show simplified or partial views, and the dimensions ofelements in the Figures may be exaggerated or otherwise not inproportion for clarity. In addition, as the terms “on,” “attached to,”or “coupled to” are used herein, one object (e.g., a material, a layer,a substrate, etc.) can be “on,” “attached to,” or “coupled to” anotherobject regardless of whether the one object is directly on, attached, orcoupled to the other object or there are one or more intervening objectsbetween the one object and the other object. Also, directions (e.g.,above, below, top, bottom, side, up, down, under, over, upper, lower,horizontal, vertical, “x,” “y,” “z,” etc.), if provided, are relativeand provided solely by way of example and for ease of illustration anddiscussion and not by way of limitation. In addition, where reference ismade to a list of elements (e.g., elements a, b, c), such reference isintended to include any one of the listed elements by itself, anycombination of less than all of the listed elements, and/or acombination of all of the listed elements.

As used herein, an “adaptive filter” is a digital filter that includes acontrol input and an adaptive algorithm that changes the filteringcharacteristics (e.g., by changing the filtering coefficients) of theadaptive filter in accordance with the control input. The filteringcharacteristics of an adaptive filter can thus be changed in accordancewith the control input. Examples of suitable adaptive algorithms includewithout limitation least mean square (LMS) algorithms, recursive leastsquare (RLS) algorithms, adaptive lattice algorithms, decision directedmean squared error algorithms, or the like. As used herein, an adaptivefilter can perform linear and/or non-linear filtering.

As used herein, “inverse distortion” combines with “distortion” tosubstantially eliminate the distortion. Also as used herein,“compensation distortion” is “inverse distortion.”

As used herein, “inherent path distortion” refers to distortion to aradio frequency (RF) signal due to the inherent operatingcharacteristics of an RF transmission path.

In some embodiments of the invention, adaptive filtering can be used tosubstantially cancel distortion in radio frequency (RF) signals. FIGS.1-6 illustrate embodiments of the invention in which adaptive filteringis used in an RF transmitting module to pre-compensate an RF signal withcompensation (inverse) distortion to cancel inherent transmission pathdistortion from the RF signal. FIGS. 7-9 illustrate embodiments of theinvention in which adaptive filtering in a multi-carrier RF receivingmodule is used to cancel from a given carrier signal distortion due tocross talk from adjacent carrier signals. FIGS. 10-13 show embodimentsof the invention in which adaptive filtering in an RF transceiver isused to cancel from a received RF signal distortion arising from leakageof a transmit signal into the receive path. FIG. 14 illustrates anembodiment of the invention in which the foregoing uses of adaptivefiltering to cancel distortion are implemented in an RF transceiver.

Turning first to FIG. 1, it is noted that FIG. 1 illustrates anembodiment of the invention in which adaptive filter is used in an RFtransmitting module to pre-compensate an RF signal with compensation(inverse) distortion to cancel inherent transmission path distortionfrom the RF signal. As shown, the transmitting module 100 of FIG. 1 caninclude a modulator 104, an adaptive filter 108, and a transmission path114, which can include transmitter components 116 and a transmittingmechanism 120. The transmitting module 100 can be part of an RFtransmitting device or an RF transceiver.

The modulator 104 can receive data 102 as input and modulate the data102 onto a carrier signal such as is known in the field. The modulator104 can thus output a modulated carrier signal 106. The data 102 can bedigital data, and the carrier signal can be a periodic RF signalsuitable for transmission. Alternatively, the data 102 can be in theform of an analog signal. Regardless, the modulator 104 can use anysuitable form of modulation including without limitation amplitudemodulation, frequency modulation, pulse code modulation, phase shiftmodulation, or the like.

As noted, the transmission path 114 can comprise transmitter components116 and a transmitting mechanism 120. An RF signal (e.g., signal 112)directed through the transmission path 114 can be radiated by thetransmitting mechanism 120 as a transmitted signal 122 into atransmission medium where it can be received by an RF receiving device(not shown in FIG. 1). The transmitter components 116 can include any ofseveral electronic hardware and/or software components for processing anRF signal for transmission by the transmitting mechanism 120. Forexample, the transmitter components 116 can include such elements as oneor more digital-to-analog converters, up converters, power amplifiers,and/or filters (e.g., band-pass filters). The transmission medium intowhich the transmitted signal 122 is transmitted can be any suitablemedium for RF signals. For example, the transmission medium can be freespace, ambient air, a cable, a telephone line, a fiber optic cable, orthe like. The transmitting mechanism 120 can be any mechanism suitablefor transmitting the RF signal into the transmission medium. Forexample, the transmitting mechanism 120 can be an RF antenna, a modem(e.g., a cable modem, a telephone line modem, a fiber optic modem), orthe like.

The transmitting module 100 can distort RF signals such that thetransmitted RF signal 122 is distorted. The transmission path 114, forexample, can introduce distortion into the signal 112, and thedistortion can be linear and/or non-linear. The transmitted signal 122can thus be a distorted version of signal 112. For example, one or moreof the transmitter components 116 (e.g., the power amplifier) canintroduce linear and/or non-linear distortion into the signal 112. Asanother example, the transmitting mechanism 120 can introduce linearand/or non-linear distortion into the signal 112. The transmitted signal122 can thus include linear and/or non-linear distortion caused by oneor more of the transmitter components 116 and/or the transmittingmechanism 120. The distortion introduced into the RF signal by thetransmission path 114 is sometimes termed “inherent path distortion”herein.

As mentioned, the transmitter components 116 can include one or morefilters, which can include a band-pass filter (not shown) thatsubstantially filters out (i.e., removes) frequencies outside thepass-band of the band-pass filter and thus passes substantially onlyfrequencies within the pass-band of the band-pass filter (not shown).Such a band-pass filter (not shown) can thus substantially canceldistortion with frequencies outside the pass-band of the filter (notshown), and the transmitted signal 122 can thus be substantially free ofdistortion with frequencies outside the pass-band of any band-passfilters (not shown) in the transmitter components 116.

Any such band-pass filters (not shown) in the transmitter components 116will not, however, cancel distortion with frequencies that are withinthe pass-band of the band-pass filters (not shown) in the transmittercomponents 116. Distortion within the pass-band are sometimes referredto herein as “in-band distortion.” Nor will such band-pass filters (notshown) in the transmitter components 116 cancel even distortion withfrequencies outside of the pass-band of the band-pass filters (notshown) caused by the transmitting mechanism 120 and/or the transmissionmedium into which the transmitted signal 122 is transmitted. Thetransmitted signal 122 can thus include both in-band and out-of-banddistortion.

An example is illustrated in FIG. 2, in which element 202 represents thepass-band of band-pass filtering components (not shown) in thetransmitter components 116 of FIG. 1. Element 206 represents in-bandlinear distortion with a frequency or frequencies inside the pass-band202, and element 208 represents in-band non-linear distortion with afrequency or frequencies inside the pass-band 202. Distortion 206 and208 can be introduced, for example, by one or more of the transmittercomponents 116 and/or the transmitting mechanism 120. Elements 204 and210 represent non-linear and linear distortion, respectively, withfrequencies outside the pass-band 202 introduced by the transmittingmechanism 120. As noted, in-band distortion 206 and 208 will typicallynot be canceled by band-pass filtering in the transmitter components116, and even out-of-band distortion 204 and 210 introduced after thetransmitter components 116 (e.g., by the transmitting mechanism 120)will typically not be removed by band-pass filtering in the transmittercomponents 116. Distortion 204, 206, 208, and/or 210—which can beexamples of components of the inherent path distortion of thetransmission path 114—can thus typically be part of the transmittedsignal 122.

Referring again to FIG. 1, the adaptive filter 108 can be configured topre-compensate the modulated carrier signal 106 with the substantialinverse of some, most, or substantially all of the inherent pathdistortion introduced into the transmitted signal 122 by thetransmission path 114 and/or other sources of distortion. The adaptivefilter 108 can thus distort the modulated carrier signal 106 withcompensation distortion, which can be the substantial inverse of theinherent path distortion introduced by the transmission path 114 and/orother sources of distortion of the transmitted signal 122. Referring tothe example illustrated in FIG. 2, the adaptive filter 108 can beconfigured to introduce into the modulated carrier signal 106 theinverse distortion of distortion 204, 206, 208, and/or 210. Thepre-compensated modulated carrier signal 112 output by the adaptivefilter 108 can thus include pre-compensation distortion that is theinverse of distortion 204, 206, 208, and/or 210 in the example in FIG.2.

In accordance with the definition of “adaptive filter” above, theadaptive filter 108 filters the modulated carrier signal 106 inaccordance with the filtering characteristics (e.g., filtercoefficients) of the adaptive filter 108, and control input 110 can varythe filtering characteristics (e.g., filter coefficients) in accordancewith an adaptive algorithm of the adaptive filter 108. One or morecontrol signals 124 (which can comprise one or more input signals) canbe provided to the control input 110 to vary the filteringcharacteristics of the adaptive filter 108 to impart the compensationdistortion to the signal 112. For example, one or more control signals124 can be provided to the control input 110 so that the adaptive filter108 introduces compensation distortion into the pre-compensated signal112 that is the inverse distortion of one or more of distortion 204,206, 208, and/or 210 in FIG. 2. Thus, as the pre-compensated signal 112passes through the transmission path 114, the inherent path distortion(e.g., 204, 206, 208, and/or 210) of the transmission path 114 can becanceled by the pre-compensation distortion introduced into thepre-compensated signal 112, and the transmitted signal 122 will besubstantially free of such distortion.

In some embodiments, the control signal 124 can be proportional to or afunction of a distorted version of the transmitted signal 122 distortedwith the inherent path distortion of the transmission path 114. Thecontrol signal 124 can be provided to the control input 110 of theadaptive filter 108, which can be configured to drive thepre-compensated signal 112 to impart inverse distortion to thepre-compensated signal 112 that is the inverse of the inherent pathdistortion imparted by the transmission path 114. More generally stated,the adaptive algorithm of the adaptive filter 108 can be configured todrive the output signal 112 to correspond to the control signal 124 orone or more features of the control signal 124.

In some embodiments, the control signal 124 provided to the controlinput 110 of the adaptive filter 108 can be an estimated or approximatedversion of the modulated carrier signal 106 distorted with the inherentpath distortion of the transmission path 114. FIG. 3 illustrates anexample 300 of the transmitting module 100 of FIG. 1 that includes atransmission path model 302 that is a model of all or part of thetransmission path 114 according to some embodiments of the invention.The transmitting module 300 of FIG. 3 thus represents on exampleconfiguration of the transmitting module 100 of FIG. 1M which thecontrol signal 124 is provided by a transmission path model 302 of allor part of the transmission path 114.

As shown in FIG. 3, the modulated carrier signal 106 can be provided toan input 304 of the transmission path model 302. As noted, thetransmission path model 302 can model all or part of the transmissionpath 114, which can thus provide at its output 306 a signal thatapproximates a version of the modulated carrier signal 106 distortedwith the inherent path distortion of the transmission path 114. That is,the transmission path model 302 can be configured to distort themodulated carrier signal 106 approximately the same as the transmissionpath 114 distorts the signal 112. The adaptive algorithm of the adaptivefilter 108 can be configured to change the filtering characteristics ofthe adaptive filter 108 in accordance with the control signal 124 todrive the signal 112 to the inverse distortion of the inherent pathdistortion of the transmission path 114. This can result, for example,in the signal 112 output by the adaptive filter 108 being the modulatedcarrier signal 106 with compensation distortion that is the inverse ofthe distortion of the inherent path distortion of the transmission path114.

The transmission path model 302 can be a digital representation of allor part of the transmission path 114, and the transmission path model302 can be obtained in any suitable fashion. For example, thetransmission path model 302 can be a computer-generated model of thetransmission path 114. As another example, the transmission path model302 can be obtained from tests of the transmission path 114 in alaboratory. Regardless, the transmission path model 302 can model bothlinear and non-linear characteristics of the transmission path 114.

As shown in FIG. 3, the transmitting module 300 can also include anelectronic memory 308 (e.g., a digital storage device) and an electroniccontroller 310 (e.g., a digital processor, computer, or the like).Multiple versions of the transmission path model 302 can be stored inthe memory 308, and the controller 310 can select any of the versions ofthe transmission path model 302 for use at any given time duringoperation of the transmitting module 300. For example, each version ofthe transmission path model 302 stored in the memory 308 can correspondto a different operating condition or combination of conditions of thetransmitting module 300, and the controller 310 can be configured toselect and change, as needed, the version of the transmission path model302 in memory 308 in accordance with the current and changingcondition(s) of the transmitting module 300. The controller 310 can thuschange the version of the transmission path model 302 used to generatedcontrol signal 124 based on changing conditions of the transmittingmodule 300. An input 312 of the controller 310 can be connected, forexample, to a sensor (not shown) that senses current condition(s) of thetransmitting module 300. Alternatively or in addition, the input 312 canallow a human operator to control the controller 310.

As just one example, each version of the transmission path model 302stored in the memory 308 can correspond to a different operatingtemperature of the transmission path 114. A temperature sensing device(not shown) for sensing the operating temperature of the transmissionpath 114 can be connected to the control input 312 of the controller310. The controller 310 can be configured to select the version of thetransmission path model 302 from the memory 308 that corresponds to thecurrent operating temperature, and the controller 310 can be furtherconfigured to change the selected version of the transmission path model302 as the operating temperature changes.

FIG. 4 illustrates an example configuration 400 of the adaptive filter108. As shown, the configuration 400 of the adaptive filter 108illustrated in FIG. 4 can include a controllable filter 402 and anadaptive module 410. The controllable filter 402 can include an input404, an output 406, and a control input 408. The controllable filter 402receives data at input 404, filters the data in accordance with thecontrol input 408, and outputs a filtered version of the data throughoutput 406. The controllable filter 402 can be a linear filter, anon-linear filter, or a combination linear/non-linear filter.

The adaptive module 410 can implement the adaptive algorithm of theadaptive filter 400. As shown, the adaptive module 410 can include adesired signal input 412, an actual signal input 414, and an erroroutput 416. The error output 416 can be a difference, or proportional ora function of the difference, between a signal at the actual signalinput 414 and a signal at the desired signal input 412. The adaptivemodule 410 can be configured to implement any suitable adaptivealgorithm including any of the adaptive algorithms identified above.

As noted, the configuration 400 shown in FIG. 4 is an exampleconfiguration of the adaptive filter 108 in FIG. 3, and theconfiguration 400 of the adaptive filter shown in FIG. 4 can thusreplace the adaptive filter 108 in FIG. 3. The input 404 of thecontrollable filter 402 can be connected to the modulated signal 106,and the output 406 of the controllable filter 402 output the compensatedsignal 112 to the transmitter components 116. The desired signal input412 of the adaptive module 410 can be connected to the output of thetransmission path model 306, and the actual signal input 414 can beconnected to the compensated signal 112. The error signal at the output416 of the adaptive module 410, which is input into the control input408 of the controllable filter 402, can control the controllable filter402. The changing error signal at the output 416 can thus change thefilter characteristics of the controllable filter 402 to drive theoutput 406—and thus the pre-compensated signal 112—to be similar to orthe same as the output 306 of the transmission path model 302.Alternatively, the filtering characteristics of the controllable filter402 and the adaptive algorithm of the adaptive module 410 can drive theoutput 406—and thus the pre-compensated signal 112—to be similar to orthe same as a feature of the output 306 of the transmission path model302.

FIG. 5 illustrates an example of the transmitting module 100 of FIG. 1in which the signal 118 is fed back from the transmission path 114 asthe control signal 124 to the control input 110 of the adaptive filter108 according to some embodiments of the invention. The signal 118 fedback as shown in FIG. 5 is thus another example of a distorted versionof the transmitted signal 122 that can be used as the control signal 124provided to the input control 110 of the adaptive filter 108. Theadaptive algorithm of the adaptive filter 108 can be configured tochange the filtering coefficients of the adaptive filter 108, inaccordance with the signal 118 fed back as the filter control signal124, to drive the signal 112 such that the signal to be transmitted 118corresponds to the modulated carrier signal 106. That is, the signal 112is driven to include compensation distortion that is the inverse of theinherent path distortion of the transmission path 114.

FIG. 6 illustrates another example configuration 600 of the adaptivefilter 108. As shown, the configuration 600 of the adaptive filter 108illustrated in FIG. 6 can include the controllable filter 402 andadaptive module 410 shown in FIG. 4 and discussed above. Theconfiguration 600 shown in FIG. 6 is an example configuration of theadaptive filter 108 in FIG. 5, and the configuration 600 of the adaptivefilter shown in FIG. 6 can thus replace the adaptive filter 108 in FIG.5.

The input 404 of the controllable filter 402 can be connected to themodulated signal 106, and the output 406 of the controllable filter 402can output the compensated signal 112 to the transmitter components 116.The desired signal input 412 of the adaptive module 410 can be connectedto the modulated signal 106, and the actual signal input 414 can beconnected to the feedback of the signal 118 from the transmission path114.

The error signal at the output 416 of the adaptive module 410, which isinput into the control input 408 of the controllable filter 402, cancontrol the controllable filter 402. The changing error signal at theoutput 416 can thus change the filter characteristics of thecontrollable filter 402 to drive the output 406—and thus thepre-compensated signal 112—so that the signal 118 is driven to be likethe modulated carrier signal 106.

The examples illustrated in FIGS. 1-6 are examples only, and variationsare possible. For example, FIGS. 1 and 3-6 show simplified blockdiagrams, and any of the transmitting modules 100, 300, and 500 caninclude additional circuitry, modules, or the like. Moreover, thetransmitting modules 100, 300, and 500 need not include each of theelements illustrated in FIGS. 1 and 3-6. As another example, the carriersignal 106 can be a multi-carrier signal that is a combination ofmultiple modulated carrier signals each having a different frequency. Itis also noted that each of the elements in FIGS. 1 and 3-6 can beimplemented in hardware circuitry, software, or a combination ofhardware and software.

Turning now to FIG. 7, it is noted that FIG. 7 illustrates an example ofa multi-carrier RF receiving module 700 that uses adaptive filtering tocancel from a given carrier signal distortion due to cross talk fromadjacent carrier signals. The module 700 can be part of an RF receivingdevice or an RF transceiver.

FIG. 7 illustrates a simplified block diagram of elements of an RFmulti-carrier receiving module 700 configured to receive and process anincoming multi-carrier RF signal 702. As is known, a multi-carrier RFsignal 702 can comprise a plurality of carrier signals each in adifferent frequency band. As shown, the RF receiving module 700 caninclude an RF receiving mechanism 704 for receiving the incomingmulti-carrier signal 702 and receiver components 706 for processing themulti-carrier signal 702 and presenting a received multi-carrier signal708 to a channelizer 710. The receiving mechanism 704 can be, forexample, an RF antenna, a modem (e.g., a cable modem, a telephone linemodem, a fiber optic modem), or the like. The receiving components 706can include such elements as one or more analog-to-digital converters,digital-to-analog converters, decoders, down converters, filters (e.g.,band-pass filters), amplifiers, or the like.

The channelizer 710 can separate the multi-carrier signal 708 from thereceiver components 706 into the individual carrier signals. Forexample, the channelizer 710 can include multiple band-pass filters (notshown) each of which passes a band of frequencies that includes one ofthe carrier signals but not the other carrier signals. The channelizer710 can output each of the separated carriers signals into one of aplurality of signal channels 712, 714, and 716.

In the example illustrated in FIG. 7, there are i number of the channels712, 714, and 716. In FIG. 7, element 712 represents a first channel,element 714 represents a second channel, and element 716 represents theith channel. Although not shown, there can be i minus 3 number ofchannels between the second channel 714 and the ith channel 716. Theincoming multi-carrier signal 702 can thus comprise as many as i numberof carrier signals.

The channelizer 710 can separate the multi-carrier signal 708 into eachof its individual carrier signals. Illustrated in FIG. 7 is a firstcarrier signal 720, a second carrier signal 740, and an ith carriersignal 760. Although not shown, there can be i minus 3 number of carriersignals between the second carrier signal 740 and the ith carrier signal760. As shown in FIG. 7, each channel 712, 714, and 716 can include ademodulator 734, 754, 774 configured to demodulate the carrier signal inthe channel 712, 714, and 716.

As is known, although the frequencies of the carrier signals 720, 740,and 760 of the multi-carrier signal 702 are in separated frequencybands, each of the carrier signals 720, 740, and 760 can includedistortion in the form of cross-talk from one or more of the othercarrier signals 720, 740, and 760. This can be referred to as cross talkdistortion. An example is illustrated in FIG. 8.

Element 802 in FIG. 8 illustrates the pass-band 802 of the first carriersignal 720. Element 804 similarly represents the pass-band 804 of thesecond carrier signal 740, and element 806 represents the pass-band ofthe ith carrier signal 760. As noted, due to cross-talk between thecarrier signals 720, 740, 760, each carrier signal 720, 740, 760 caninclude cross talk distortion in the form of cross talk from the othercarrier signals 720, 740, 760.

Thus, as illustrated in FIG. 8, the first carrier signal 720 can includedistortion 810 arising from all or part of the second carrier signal 740leaking into the carrier signal 720 due to cross talk. As alsoillustrated, the first carrier signal 720 can also include distortion812 arising from all or part of the ith carrier signal 760 leaking intothe first carrier signal 720 due to cross talk. As shown, suchdistortion 810, 812 can include components with frequencies in thepass-band 802 of the first carrier signal 720. Moreover, such distortion810, 812 can be linear or non-linear or a combination of linear andnon-linear distortion. FIG. 8 also illustrates the second carrier signal740 with distortion 808 arising from all or part of the first carriersignal 720 leaking into the second carrier signal 740 due to cross talkand with distortion 812 from the ith carrier signal 760 leaking in wholeor part into the second carrier signal 740 as generally discussed above.As shown, such distortion 808, 812 can include components withfrequencies in the pass-band 804 of the second carrier signal 740. Theith carrier signal 720 is also illustrated with distortion 808 from thefirst carrier signal 720 leaking in whole or part into the ith carriersignal 760 as generally discussed above and with distortion 810 from thesecond carrier signal 740 leaking in whole or part into the ith carriersignal 760 also as generally discussed above. As shown, such distortion808, 810 can include components with frequencies in the pass-band 806 ofthe ith carrier signal 760.

As shown in FIG. 7, the multi-carrier receiving module 700 can includein each of the channels 712, 714, 716 a subtractor 730, 750, 770 and oneor more adaptive filters 724, 744, 764 configured in an adaptive noisecancellation configuration to substantially cancel the cross talkdistortion 808, 810, 812 from the carrier signals 720, 740, 760.

For example, the first channel 712 can include a subtractor 730 and atleast one adaptive filter 724. Distortion (e.g., 810, 812) in the firstcarrier signal 720 from cross talk from another one of the carriersignals (e.g., the first carrier signal 740 or the second carrier signal760) can be canceled from the first carrier signal 720 by connecting theother one of the carrier signals to the input 722 of the adaptive filter724 and then subtracting (in the subtractor 730) the output 728 of theadaptive filter 724 from the first carrier signal 720 as shown in FIG.7. As also shown, the output 732 of the subtractor 730 can be fed backto the control input 726 of the adaptive filter 724. The adaptivealgorithm of the adaptive filter 724 can tend to cancel the distortionin the first carrier signal 720 that are due to cross talk from thecarrier signal connected to the input 722 of the adaptive filter 724.Suitable adaptive algorithms for doing so include those identifiedabove. The distortion in the first carrier signal 720 due to cross talkfrom one of the other carrier signals can thus be canceled from thefirst carrier signal 720. The output 732 of the subtractor 730 can thusbe the first carrier signal 720 with such cross talk distortioncanceled.

Although not shown, there can be additional adaptive filters 724 in thefirst channel 712. The input 722 of each such additional adaptive filter724 can be connected to a different one of the other carrier signals(other than the first carrier signal 720) but otherwise configured andconnected as shown in FIG. 7. Such additional adaptive filters 724 canthus cancel from the first carrier signal 720 distortion (e.g., 810,812) in the first carrier signal 720 due to cross talk from multipleones of the other carrier signals.

As shown in FIG. 7, the second channel 714 can similarly include asubtractor 750 (which can be like subtractor 730) and at least oneadaptive filter 744 (which can be like adaptive filter 744) with aninput 742 connected to one of the carrier signals other than the secondcarrier signal 740. The output 748 of the adaptive filter 744 can besubtracted by subtractor 750 from the second carrier signal 740. Withthe output 752 of the subtractor 750 connected to the control input 746of the adaptive filter 744, the adaptive algorithm (which can be any ofthe adaptive algorithms referenced above with respect to adaptive filter724) can cancel the distortion in the second carrier signal 740 that aredue to cross talk from the other carrier signal connected to the input742 of the adaptive filter 744. Multiple such adaptive filters 744 canbe connected to multiple ones of the other carrier signals (carrierssignals other than the second carrier signal) to similarly canceldistortion (e.g., 808, 812) in the second carrier signal 740 due tocross talk from those other carrier signals.

Still referring to FIG. 7, the ith channel 716 can also include asubtractor 770 (which can be like subtractor 730) and one or moreadaptive filters 764 (which can be like adaptive filter 724) each withan input 762 connected to one of the carrier signals other than the ithcarrier signal 760. Generally in accordance with the discussions aboveregarding the first channel 712 and the second channel 714, theoutput(s) 768 of the adaptive filter(s) 764 can be subtracted bysubtractor 770 from the ith carrier signal 760, and the output 772 ofthe subtractor 770 can be connected to the control input(s) 766 of theadaptive filter(s) 764, which can cancel the distortion (e.g., 808, 810)in the ith carrier signal 760 that are due to cross talk from the othercarrier signal(s) connected to the input(s) 762 of the adaptivefilter(s) 764.

FIG. 9 illustrates an example in which the receiving module 700′ of FIG.7 has three channels such that the ith channel 716 is the third channeland the ith carrier signal 760 is the third carrier signal. (The ithchannel 716 is thus referred to as the third channel 716 and the ithcarrier signal 760 is referred to as the third carrier signal 760 whendiscussing FIG. 9.) Moreover, in the example shown in FIG. 9, eachchannel 712, 714, and 716 includes an adaptive filter 724, 744, 764 tocancel cross talk distortion from each of the other carrier signals.

As shown, the first channel 712 includes an adaptive filter 724, 724′for each of the other carrier signals 740 and 760 (which are the carriersignals other than the first carrier signal 720). The input 722 of theadaptive filter 724 is connected to the second carrier signal 740, andthe input 722′ of the adaptive filter 724′ is connected to the thirdcarrier signal 760. The subtractor 730 subtracts the outputs 728 and728′ of the adaptive filters 724 and 724′ from the first carrier signal720 as shown in FIG. 9. With the output 732 of the subtractor 730connected to the control inputs 726 and 726′ of the adaptive filters 724and 724′, the combination of the subtractor 730 and the adaptive filters724 and 724′ tends to cancel distortion in the first carrier signal 720due to cross talk from the second carrier signal 740 and the thirdcarrier signal 760. The output 732 of the subtractor 730 can thus bedriven to be a version of the first carrier signal 720 that issubstantially free of distortion due to cross talk from the secondcarrier signal 740 and the third carrier signal 760.

Similarly, the second channel 714 includes an adaptive filter 744, 744′for each of the other carrier signals 720 and 760 (which are the carriersignals other than the second carrier signal 740). The input 742 of theadaptive filter 744 is connected to the first carrier signal 720, andthe input 742′ of the adaptive filter 744′ is connected to the thirdcarrier signal 760. The subtractor 750 subtracts the outputs 748 and748′ of the adaptive filters 744 and 744′ from the second carrier signal740 as shown in FIG. 9, and with the output 752 of the subtractor 750connected to the control inputs 746 and 746′ of the adaptive filters 744and 744′, the combination of the subtractor 750 and the adaptive filters744 and 744′ tends to cancel distortion in the second carrier signal 740due to cross talk from the first carrier signal 720 and the thirdcarrier signal 760. The output 752 of the subtractor 750 can thus bedriven to be a version of the second carrier signal 740 that issubstantially free of distortion due to cross talk from the firstcarrier signal 720 and the third carrier signal 760.

Likewise, the third channel 716 includes an adaptive filter 764, 764′for each of the other carrier signals 720 and 740 (which are the carriersignals other than the third carrier signal 760). The input 762 of theadaptive filter 764 is connected to the first carrier signal 720, andthe input 762′ of the adaptive filter 764′ is connected to the secondcarrier signal 740. The subtractor 770 subtracts the outputs 768 and768′ of the adaptive filters 764 and 764′ from the third carrier signal760 as shown in FIG. 9. With the output 772 of the subtractor 770connected to the control inputs 766 and 766′ of the adaptive filters 764and 764′, the combination of the subtractor 770 and the adaptive filters764 and 764′ tends to cancel distortion in the third carrier signal 760due to cross talk from the first carrier signal 720 and the secondcarrier signal 740. The output 772 of the subtractor 770 can thus bedriven to be a version of the second carrier signal 760 that issubstantially free of distortion due to cross talk from the firstcarrier signal 720 and the second carrier signal 740.

The adaptive filters 724 and 724′ in FIG. 9 can be implemented like theadaptive filter 400 shown in FIG. 4. That is, each of adaptive filters724 and 724′ can include the controllable filter 402 and adaptive module410 shown in FIG. 4 and discussed above. Implementing adaptive filter724, the input 404 and output 406 of the of the controllable filter 402,and the desired input 412 and actual input 414 of the adaptive module410 can be connected in FIG. 9 as follows: the second carrier signal 740can be connected to the input 404 and the actual signal input 414; theoutput 406 can be connected as 728 to the subtractor 730; and the output732 of the subtractor 730 can be connected to the desired signal input412. Implementing the adaptive filter 724′, the input 404 and output 406of the of the controllable filter 402, and the desired input 412 andactual input 414 of the adaptive module 410 can be connected in FIG. 9as follows: the third carrier signal 760 can be connected to the input404 and the actual signal input 414; the output 406 can be connected as728′ to the subtractor 730; and the output 732 of the subtractor 730 canbe connected to the desired signal input 412. The adaptive filters 744,744′, 764, and 764′ can similarly be implemented like the adaptivefilter 400 shown in FIG. 4.

The depiction of the multi-carrier module 700 and 700′ in FIGS. 7 and 9is an example only, and variations are possible. For example, FIGS. 7and 9 show simplified block diagrams, and the receiving modules 700 and700′ can include additional circuitry, modules, or the like. Moreover,the receiving modules 700 and 700′ need not include each of the elementsillustrated in FIGS. 1 and 3-6. As another example, although threechannels 712, 714, and 716 for three carrier signals 720, 740, and 760are illustrated, there can be fewer or more channels and carriersignals. As yet another example, the output 736 of the demodulator 734rather than the output 732 of the subtractor 730 in the first channel712 can be connected to the control input(s) 724 of the adaptivefilter(s) 724. Similarly, the output 756 of the demodulator 754 ratherthan the output 752 of the subtractor 750 in the second channel 714 canbe connected to the control input(s) 744 of the adaptive filter(s) 744,and the output 776 of the demodulator 774 rather than the output 772 ofthe subtractor 770 in the ith channel 714 (or the third channel 716 inFIG. 9) can be connected to the control input(s) 766 of the adaptivefilter(s) 764. It is also noted that each of the elements in FIGS. 7 and9 can be implemented in hardware circuitry, software, or a combinationof hardware and software.

Turning next to FIG. 10, it is noted that FIG. 10 shows an example of anRF transceiver 1000 that uses adaptive filtering to cancel from areceived RF signal distortion arising from leakage of a transmit signalinto the receive path. As is known, an RF transceiver is a device thatis capable of both transmitting and receiving RF signals. As such, theRF transceiver 1000 of FIG. 10 can include an RF transmitter 1001 and anRF receiver 1003.

The RF transmitter 1001 can include an RF modulator 1004, which canreceive data 1002 as input and modulate the data 1002 onto a carriersignal. The modulator 1004 and the data 1002 can be generally like themodulator 104 and data 102 discussed above with respect to FIG. 1. Themodulator 1004 can output a modulated carrier signal 1006. As also shownin FIG. 10, the transmitter 1001 can also include a transmission path1008, which can comprise transmitter components 1010 and atransmitting/receiving mechanism 1014. Directed through the transmissionpath 1008, the modulated carrier signal 1006 can be radiated by thetransmitting/receiving mechanism 1014 as a transmitted signal 1016 intoa transmission medium where it can be received by a different RFreceiving device (not shown in FIG. 10), which can be remotely located.

The transmitter components 1010 can be the same as or similar to thetransmitter components 116 of FIG. 1 and can include any of thecomponents mentioned above with respect to the transmitter components116 of FIG. 1. The transmission medium into which the transmitted signal1016 is transmitted can be any suitable medium for RF signals including,without limitation, free space, ambient air, a cable, a telephone line,a fiber optic cable, or the like. The transmitting/receiving mechanism1014 can be any mechanism suitable for transmitting the RF signal 1016into the transmission medium and, as will be discussed, receiving anincoming RF signal 1018. The transmitting/receiving mechanism 1014 cancomprise a single apparatus for transmitting and receiving RF signals,or the transmitting/receiving mechanism 1014 can comprise one device fortransmitting RF signals and another device for receiving RF signals.Regardless, examples of a suitable transmitting/receiving mechanism 1014include an RF antenna, a modem (e.g., a cable modem, a telephone linemodem, a fiber optic modem), or the like.

The RF receiver 1003 can include the transmitting/receiving mechanism1014 and a receive path 1022, which can comprise thetransmitting/receiving mechanism 1014 and receiver components 1024. Thatis, an incoming RF signal 1018 (which can be an RF signal transmitted bya different RF device (not shown) remotely located from the transceiver1000) can be received by the transmitting/receiving mechanism 1014 andprovided as a received RF signal 1020 to the receiver components 1024.The receiver components 1024 can include such elements as one or moreanalog-to-digital converters, digital-to-analog converters, decoders,down converters, amplifiers, filters (e.g., band-pass filters), and/orthe like. As shown, the receiver 1003 can also include a demodulator1040 for demodulating the received RF signal to produce data 1042 in theRF signal 1118.

Typically, the carrier signal of the transmitted RF signal 1016 is in adifferent frequency band than the carrier signal of the incoming RFsignal 1018. For example, as illustrated in FIG. 11, the transmittedsignal 1016 can have a frequency in a transmission pass-band 1102 thatis spaced apart from (and thus does not overlap) the pass-band 1104 ofthe incoming signal 1018. Band-pass filtering (not shown) in thetransmitter components 1010 can remove frequencies from the RF signal tobe transmitted 1012 so that the transmitted signal 1016 does not includefrequencies outside the pass-band 1102.

All or part of the modulated RF signal 1006 or 1012 can neverthelessleak from the transmitter 1001 into the receiver 1003. For example, allor part of the RF signal 1006 or 1012 can leak from the transmissionpath 1008 into the receive path 1022. Such a leaked transmission signalis labeled 1044 in FIG. 10. The received RF signal 1020 or 1026 can thusinclude distortion in the arising from a leaked transmission signal1044.

As noted, the receiver components 1024 can include a band-pass filter(not shown) that substantially filters out (i.e., removes) frequenciesfrom the received signal 1020 that are outside the pass-band 1104 of theof the band-pass filter (not shown) in the receiver components 1024.Distortion, including distortion arising from the leaked transmissionsignal 1044, with frequencies outside the pass-band 1104 of theband-pass filter (not shown) in the receiver components 1024 can thus beremoved from the signal 1026 output by the receiver components 1024. Theleaked transmission signal 1044 can, however, cause in-band distortion,that is, distortion with frequencies inside the pass-band 1104 of theband-pass filter (not shown) in the receiver components 1024. Forexample, distortion 1106 (which can include linear and/or non-lineardistortion) in FIG. 11 is inside the pass-band 1104 and thus will not beremoved by band-pass filtering in the receiver components 1024.

As shown in FIG. 10, the receiver 1003 can include a subtractor 1028 andan adaptive filter 1030 configured in an adaptive noise cancellationconfiguration to substantially cancel the distortion 1106 caused by theleaked transmission signal 1044. As shown, an approximated distortionsignal 1032 approximating the leaked transmission signal 1044 can beprovided as the input to the adaptive filter 1030, and the output 1036of the adaptive filter 1030 can be subtracted by the subtractor 1028from the received signal 1026. The output 1038 of the subtractor 1028can be provided as the control input 1034 to the adaptive filter 1030.The adaptive module of the adaptive filter 1030 can be configured tocancel the distortion (e.g., the distortion 1106 in FIG. 11) in thereceived signal 1026 (which can be a wideband signal in someembodiments) that is due to the leaked transmission signal 1044.Suitable adaptive algorithms for doing so include those identifiedabove. The output 1038 of the subtractor 1028 can thus be the receivedsignal 1026 with distortion (e.g., 1106 in FIG. 11) caused by the leakedtransmission signal 1044 substantially canceled.

The approximated distortion signal 1032 that approximates the leakedtransmission signal 1044 and is provided as input to the adaptive filter1030 in FIG. 10 can be obtained in any suitable manner.

FIG. 12 illustrates an example configuration 1200 of the transceiver1000 of FIG. 10 that includes a transmission path model 1202 that is amodel all or part of the transmission path 1008 (which as noted caninclude transmitter components 1010 and the transmitting/receivingmechanism 1014) for providing the approximated distortion signal 1032according to some embodiments of the invention. The transceiver 1200 ofFIG. 12 thus represents on example configuration of the transceiver 1000of FIG. 10 in which the approximated distortion signal 1032 is providedby a transmission path model 1202.

As shown in FIG. 12, the modulated carrier signal 1006 can be providedto an input 1204 of the transmission path model 1202. The transmissionpath model 1202 can model all or part of the transmission path 1008 andcan thus provide at its output 1206 a signal that approximates thecarrier signal 1006 after passing through all or part of thetransmission path 1008. The output 1206 of the transmission path model1202 can thus approximate the leaked transmission signal 1044 and canthus be the approximated distortion signal 1032 provided to the input ofthe adaptive filter 1030 as shown in FIG. 12.

The transmission path model 1202 can be generally the same as or similarto the transmission path model 302 discussed above with respect to FIG.3. For example, the transmission path model 1202 can be acomputer-generated model of all or part of the transmission path 1008.As another example, the transmission path model 1202 can be obtainedfrom tests of the transmission path 1008 in a laboratory. Regardless,the transmission path model 1202 can model both linear and non-linearcharacteristics of the transmission path 1008.

Similar to the module 300 shown in FIG. 3, the transceiver 1200 of FIG.12 can also include an electronic memory 1208 (which can be the same asor similar to the memory 308 in FIG. 3) and a controller 1210 (which canbe the same as or similar to the controller 310 in FIG. 3). Generally inaccordance with the discussion above of memory 308 and control 310 inFIG. 3, multiple versions of the transmission path model 1202 can bestored in the memory 1208, and the controller 1210 can select any of theversions of the transmission path model 1202 for use at any given timeduring operation of the transmitting device 1200. For example, eachversion of the transmission path model 1202 stored in the memory 1208can correspond to a different operating condition or conditions of thetransmitting device 1200, and the controller 1210 can be configured toselect and change, as needed, the version of the transmission path model1202 in memory 1208 in accordance with the current condition orconditions of the transmitting device 1200. The controller 1210 can thuschange the version of the transmission path model 1202 used to generatedthe approximated distortion signal 1032 based on changing conditions ofthe transmitting device 1200. An input 1212 of the controller 1210 canbe connected, for example, to a sensor (not shown) that senses a currentcondition or conditions of the transmitting device 1200. Alternativelyor in addition, the input 1212 can allow a human operator to control thecontroller 1210.

Again generally in accordance with the discussion above of transmissionpath model, 302, memory 308, and controller 310 in FIG. 3, each versionof the transmission path model 1202 stored in the memory 1208 cancorrespond to, for example, a different operating temperature of thetransmission path 1008. A temperature sensing device (not shown) can beconnected to the control input 1212 of the controller 1210. Thecontroller 1210 can be configured to select the version of thetransmission path model 1202 from the memory 1208 that corresponds tothe current operating temperature, and the controller 1210 can befurther configured to change the selected version of the transmissionpath model 1202 as the operating temperature changes.

The adaptive filter 1030 in FIG. 12 can be implemented like the adaptivefilter 400 shown in FIG. 4. That is, the adaptive filter 1030 caninclude the controllable filter 402 and adaptive module 410 shown inFIG. 4 and discussed above. The input 404 and output of the controllablefilter 402, and the desired input 412 and actual input 414 of theadaptive module 410 can be connected in FIG. 12 as follows: the output1206 of the transmission path model 1202 can be connected to the input404 and the actual signal input 414; the output 406 can be connected as1036 to the subtractor 1028; and the output 1038 of the subtractor 1028can be connected to the desired signal input 412.

FIG. 13 illustrates an example 1300 of the transceiver 1000 of FIG. 10in which the signal 1012 is fed back from the transmission path 1008 andprovided as the approximated distortion signal 1032 input to theadaptive filter 1030 according to some embodiments of the invention. Thesignal 1012 fed back as shown in FIG. 13 is thus another example of anapproximated distortion signal 1032 that can be provided as input to theadaptive filter 1030. The transmitting module 1300 of FIG. 13 thusrepresents an example configuration of the transmitting module 1000 ofFIG. 10 in which the approximated distortion signal 1032 is provided bya feedback signal from the transmission path 1008.

The adaptive filter 1030 in FIG. 13 can also be implemented like theadaptive filter 400 shown in FIG. 4. That is, the adaptive filter 1030can include the controllable filter 402 and adaptive module 410 shown inFIG. 4 and discussed above. The input 404 and output of the of thecontrollable filter 402, and the desired input 412 and actual input 414of the adaptive module 410 can be connected in FIG. 13 as follows: thefeedback of signal 1012 from the transmission path 1008 can be connectedto the input 404 and the actual signal input 414; the output 406 can beconnected as 1036 to the subtractor 1028; and the output 1038 of thesubtractor 1028 can be connected to the desired signal input 412.

The examples illustrated in FIGS. 10-13 are examples only, andvariations are possible. For example, FIGS. 10, 12, and 13 showsimplified block diagrams, and any of the transceivers 1000, 1200, and1300 can include additional circuitry, modules, or the like. Moreover,the transceivers 1000, 1200, and 1300 need not include each of theelements illustrated in FIGS. 10, 12, and 13. As another example, thecarrier signal 1006 can be a multi-carrier signal that is a combinationof multiple modulated carrier signals each having a different frequency.It is also noted that each of the elements in FIGS. 10, 12, and 13 canbe implemented in hardware circuitry, software, or a combination ofhardware and software.

Two or more of the techniques for canceling distortion in RF signalsdiscussed above can be used in combination in the same RF device. FIG.14 illustrates an example in which adaptive filtering is used topre-compensate an RF signal to cancel transmission path distortion froman RF signal to be transmitted (see FIGS. 1-6), adaptive filtering isused to cancel from a given carrier signal distortion due to cross talkfrom adjacent carrier signals in a received multicarrier RF signal (seeFIGS. 7-9), and adaptive filtering is used to cancel from a received RFsignal distortion arising from leakage of a transmit signal into thereceiver path (see FIGS. 10-13).

As shown in FIG. 14, an RF transceiver 1400 can include a transmitter1401 and a receiver 1403. The transmitter 1401 can include a modulator1404, an adaptive filter 1408, and a transmission path 1414 (which caninclude transmission components 1416 (which can be the same as orsimilar to the transmission components 116 of FIG. 1) and atransmitting/receiving device 1420). The modulator 1404, adaptive filter1408, and transmission path 1414 can function and be the same as orsimilar to the modulator 104, adaptive filter 108, and transmission path114 of FIG. 1 as described above including variations and examplesillustrated in FIGS. 2-6, and the transmitting/receiving device 1420 canfunction and be the same as or similar to the transmitting/receivingdevice 1020 in FIG. 10. That is, the modulator 1404 can modulate data1402 into a carrier signal and output a modulated carrier signal 1406.The modulated carrier signal 1406 can be filtered by an adaptive filter1408 under control of a control signal 1424 at a control input 1410 ofthe adaptive filter 1408. The control signal 1424 can be the same as orsimilar to control signal 124 of FIG. 1 as described above. That is, canbe an estimated or approximated version of the modulated carrier signal1406 distorted with the inherent path distortion of the transmissionpath 1414.

The adaptive filter 1408 can function and be the same as or similar tothe adaptive filter 108 in FIG. 1 as discussed above. That is, theadaptive filter 1408 can be configured and operated to pre-compensatethe modulated carrier signal 1406 with an inverse of the inherent pathdistortion imparted by the transmission path 1414. The pre-compensatedsignal 1412 output by the adaptive filter 1408 thus includes inversedistortion that cancels the inherent path distortion imparted to thesignal 1412 by the transmission path 1414. The transmitted signal 1422can thus be substantially free of the inherent path distortion impartedby the transmission path 1414. The transmitter 1401 can thus implementthe use of adaptive filtering to pre-compensate an RF signal to betransmitted to cancel transmission path distortion from the transmittedRF signal illustrated in and discussed above with respect to FIGS. 1-6.

The receiver 1403 can be a multi-carrier receiver, which can begenerally similar to or the same as the multi-carrier receivers 700 and700′ illustrated in and discussed above with respect to FIGS. 7-9. Asshown, the transmitter 1403 can include a receive path 1504 comprisingthe transmitting/receiving mechanism 1420 and receiver components 1506.The receive path 1504 can function and be the same as or similar toreceive path 1022 in FIG. 10. That is, an incoming multi-carrier signal1502 can be received by the transmitting/receiving mechanism 1420 andprocessed by the receiver components 1506 to produce a receivedmulti-carrier signal 1508. The receiver components 1506 can function andbe the same as or similar to the receiver components 706 of FIG. 7 asdescribed above, and the multi-carrier signal 1508 can be the same as orsimilar to the multi-carrier signal 708 of FIG. 7 as described above.

As also shown in FIG. 14, the multi-carrier receiver 1403 can include achannelizer 1510 and a plurality of channels 1512 (a first channel),1516 (an ith channel), which can function and be the same as or similarto the channelizer 710 and channels 712, 714, 716 in FIGS. 7 and 9 asdescribed above. (There can be i minus 2 number of additional channelsbetween the first channel 1512 and the ith channel 1516.) That is, thechannelizer 1510 can separate the multi-carrier signal 1508 into itsconstituent carrier signals 1520 (a first carrier signal), 1560 (an ithcarrier signal), which can be like any of carrier signals 720, 740, 760generally as discussed above with respect to FIGS. 7-9. (Themulticarrier signal 1508 can have minus 2 number of additional carriersignals the first carrier signal 1520 and the ith carrier signal 1560.)

The first channel 1512 can include a subtractor 1530 and an adaptivefilter 1524 having an input 1522, and output 1528, and a control input1526. The subtractor 1530 can function and be the same as or similar tothe subtractor 730 in FIGS. 7 and 9 as described above, and the adaptivefilter 1524 can function and be the same as or similar to the adaptivefilter 724 in FIGS. 7 and 9 as described above. That is, the ith carriersignal 1560 can be provided to the input 1522 of the adaptive filter1524, and the subtractor 1530 can subtract the output 1528 of theadaptive filter 1524 from the first carrier signal 1520. And the output1532 of the subtractor 1530 can be fed back to the control input 1526 ofthe adaptive filter 1524, which can vary the filtering characteristicsof the adaptive filter 1524 such that the output 1532 of the subtractor1530 converges on the first carrier signal 1520 absent cross talkdistortion from the ith carrier signal 1560. The first channel 1512 cansimilarly include additional adaptive filters 1524 with their inputsconnected to other carrier signals (any or all of the carrier signalsbetween the first carrier signal 1520 and the ith carrier signal 1560)to cancel cross talk in the first carrier signal 1520 due to cross talkfor the other carrier signals generally as discussed above with respectto FIGS. 7-9.

The ith channel 1516 can similarly include a subtractor 1570 and anadaptive filter 1564 having an input 1562, an output 1568, and a controlinput 1566. The subtractor 1570 can function and be the same as orsimilar to the subtractor 770 in FIGS. 7 and 9 as described above, andthe adaptive filter 1564 can function and be the same as or similar tothe adaptive filter 764 in FIGS. 7 and 9 as described above. That is,the first carrier signal 1520 can be provided to the input 1562 of theadaptive filter 1564, and the subtractor 1570 can subtract the output1568 of the adaptive filter 1564 from the ith carrier signal 1560. Theoutput 1572 of the subtractor 1570 can be fed back to the control input1566 of the adaptive filter 1564, which can vary the filteringcharacteristics of the adaptive filter 1564 such that the output 1572 ofthe subtractor 1570 converges on the ith carrier signal 1560 absentcross talk distortion from the first carrier signal 1520. The ithchannel 1516 can similarly include additional adaptive filters 1564 withtheir inputs connected to other carrier signals (any or all of thecarrier signals between the first carrier signal 1520 and the ithcarrier signal 1560) to cancel cross talk in the ith carrier signal 1560due to cross talk for the other carrier signals generally as discussedabove with respect to FIGS. 7-9.

Each carrier signal 1520 to 1560 can thus be substantially free of thedistortion imparted by cross talk from the other carrier signal(s). Thereceiver 1403 can thus implement the use of adaptive filtering to cancelcross talk distortion from the carriers separated from a receivedmulti-carrier signal 1508 as illustrated in and discussed with respectto FIGS. 7-9 above.

As shown in FIG. 14, the receiver 1403 can also include an adaptivefilter 1630, 1730 in each channel 1512, 1516 to cancel distortion ineach of the carrier signals 1520, 1560 arising from a leakedtransmission signal 1750 (which can be the same as or similar to theleaked transmission signal 1044) from the transmission path 1414 intothe receive path 1504 generally as discussed above with respect to FIGS.10-13.

For example, the receiver 1403 can also include an adaptive filter 1630having an input 1632, an output 1636, and a control input 1634. Theadaptive filter 1630 can function and be the same as or similar to theadaptive filter 1030 in FIGS. 10, 12, and 13 as described above. Thatis, the control signal 1424 (which can be the same as the approximateddistortion signal 1032 discussed above with respect to FIGS. 10-13) canbe provided as input 1632 to the adaptive filter 1630, and the output1636 can be subtracted by the subtractor 1530 from the first carriersignal 1520. The output 1532 of the subtractor 1530 can be fed back tothe control input 1634 of the adaptive filter 1630, which can vary thefiltering characteristics of the adaptive filter 1630 such that theoutput 1532 of the subtractor 1530 converges on the first carrier signal1520 absent distortion from the leaked transmission signal 1750 (whichcan be the same as or similar to the transmit signal leakage 1044 inFIGS. 10, 12, and 13 as described above) from the first carrier signal1520. The receiver 1403 can thus implement the use of adaptive filteringto cancel distortion in the first carrier signal 1520 that arises fromthe leaked transmission signal 1750 from the transmission path 1414 intothe receive path 1504 generally as illustrated in and discussed abovewith respect to FIGS. 10-13.

The receiver 1403 can also include an adaptive filter 1730 having aninput 1732, an output 1736, and a control input 1734. The adaptivefilter 1730 can function and be the same as or similar to the adaptivefilter 1030 in FIGS. 10, 12, and 13 as described above. That is, thecontrol signal 1424 (which can be the same as the approximateddistortion signal 1032 discussed above with respect to FIGS. 10-13) canbe provided as input 1732 to the adaptive filter 1730, and the output1736 can be subtracted by the subtractor 1570 from the ith carriersignal 1560. The output 1572 of the subtractor 1570 can be fed back tothe control input 1734 of the adaptive filter 1730, which can vary thefiltering characteristics of the adaptive filter 1730 such that theoutput 1572 of the subtractor 1570 converges on the ith carrier signal1560 absent distortion from the leaked transmission signal 1750 (whichcan be the same as or similar to the transmit signal leakage 1044 inFIGS. 10, 12, and 13 as described above) from the ith carrier signal15260. The receiver 1403 can thus implement the use of adaptivefiltering to cancel distortion in the ith carrier signal 1560 thatarises from the leaked transmission signal 1750 from the transmissionpath 1414 into the receive path 1504 generally as illustrated in anddiscussed above with respect to FIGS. 10-13 above.

The example illustrated in FIG. 14 is an example only, and variationsare possible. For example, FIG. 14 shows simplified block diagrams, andthe transceiver 1400 can include additional circuitry, modules, or thelike. Moreover, the transmitting device 1400 need not include each ofthe elements illustrated in FIG. 14. As another example, the carriersignal 1406 can be a multi-carrier signal that is a combination ofmultiple modulated carrier signals each having a different frequency. Itis also noted that each of the elements in FIG. 14 can be implemented inhardware circuitry, software, or a combination of hardware and software.

Although specific embodiments and applications of the invention havebeen described in this specification, these embodiments and applicationsare exemplary only, and many variations are possible.

We claim:
 1. A radio frequency (RF) transceiver comprising: an RFtransmitter configured to transmit RF signals; an RF receiver configuredto receive incoming RF signals, wherein said RF receiver comprises: anadaptive filter configured to filter, in accordance with a variablefiltering characteristic, a distortion signal, wherein said distortionsignal corresponds to a transmission path RF signal transmitted by saidRF signal, and a subtractor configured to subtract from a received RFsignal received by said RF receiver an output of said adaptive filter,wherein said distortion signal is an output of a model of a transmissionpath of said RF transmitter and an input of said model is connected tosaid RF transmitter to receive an RF signal from said RF transmitter; anelectronic memory in which are stored different versions of said modelof said transmission path of said RF transmitter, wherein each saidversion of said model corresponds to a different state of said RFtransmitter; and an electronic controller configured to: identify acurrent state of said RF transmitter, and select one of said versions ofsaid model as a selected model, wherein said distortion signal is anoutput of said selected model.
 2. The transceiver of claim 1, wherein:said adaptive filter comprises a control input, said adaptive filter isconfigured to vary said variable filtering characteristic in accordancewith said control input, and an output of said subtractor is connectedto said control input.
 3. The transceiver of claim 1, wherein: said RFreceiver is further configured to receive a multicarrier RF signalcomprising carrier signals each having a frequency within a differentfrequency pass-band, and said RF receiver comprises RF channels eachconfigured for one of said carrier signals.
 4. The transceiver of claim3, wherein: said adaptive filter is a first adaptive filter disposed ina first one of said channels, and said variable filtering characteristicis a first variable filtering characteristic, said received RF signal isa first one of said carrier signals in said first one of said channels,said subtractor is a first subtractor disposed in said first one of saidchannels and is configured to subtract said output of said firstadaptive filter from said first one of said carrier signals; and whereinsaid RF receiver further comprises: a second adaptive filter disposed ina second one of said channels and configured to filter, in accordancewith a second variable filtering characteristic, said distortion signal;and a second subtractor disposed in said second one of said channels andconfigured to subtract an output of said second adaptive filter from asecond one of said carrier signals, which is in said second one of saidchannels.
 5. The transceiver of claim 4, wherein: said first adaptivefilter comprises a control input, and said first adaptive filter isconfigured to vary said first variable filtering characteristic inaccordance with said control input of said first adaptive filter; anoutput of said first subtractor is connected to said control input ofsaid first adaptive filter; said second adaptive filter comprises acontrol input, and said second adaptive filter is configured to varysaid second variable filtering characteristic in accordance with saidcontrol input of said second adaptive filter; and an output of saidsecond subtractor is connected to said control input of said secondadaptive filter.
 6. The transceiver of claim 5, wherein said RF receiverfurther comprises a third adaptive filter, which is disposed in saidfirst channel, said third adaptive filter configured to filter inaccordance with a third variable filtering characteristic said secondone of said carrier signals, wherein said first subtractor is furtherconfigured to subtract an output of said third adaptive filter from saidfirst one of said carrier signals.
 7. The transceiver of claim 6,wherein said RF receiver further comprises a fourth adaptive filter,which is disposed in said second channel, said fourth adaptive filterconfigured to filter in accordance with a fourth variable filteringcharacteristic said first one of said carrier signals, wherein saidsecond subtractor is further configured to subtract an output of saidfourth adaptive filter from said second one of said carrier signals. 8.The transceiver of claim 7, wherein: said third adaptive filtercomprises a control input, and said third adaptive filter is configuredto vary said third variable filtering characteristic in accordance withsaid control input of said third adaptive filter; an output of saidfirst subtractor is connected to said control input of said thirdadaptive filter; said fourth adaptive filter comprises a control input,and said fourth adaptive filter is configured to vary said fourthvariable filtering characteristic in accordance with said control inputof said fourth adaptive filter; and an output of said second subtractoris connected to said control input of said fourth adaptive filter. 9.The transceiver of claim 1, wherein: said pre-compensation filter is apre-compensation adaptive filter configured to filter, in accordancewith a variable filtering characteristic, said outgoing RF signals, andsaid pre-compensation adaptive filter is configured to vary saidvariable filtering characteristic of said pre-compensation adaptivefilter in accordance with said distortion signal.
 10. A process ofcanceling transmit signal leakage distortion from a received RF signalin an RF transceiver comprising an RF transmitter and an RF receiver,said process comprising: receiving a multicarrier RF signal at said RFtransceiver, wherein said multicarrier RF signal comprises a pluralityof carrier signals each having a different frequency in a differentfrequency pass-band; separating said multicarrier RF signal into a firstone of said carrier signals and a second one of said carrier signals,wherein said first one of said carrier signals is a different carriersignal with a different frequency in a different frequency pass-bandthan said second one of said carrier signals; providing a distortionsignal to a first adaptive filter and a second adaptive filter;filtering said distortion signal with said first adaptive filter;subtracting an output of said first adaptive filter from said first oneof said carrier signals; filtering said distortion signal with saidsecond adaptive filter; and subtracting an output of said secondadaptive filter from said second one of said carrier signals, wherein:said distortion signal is an output of said RF transmitter to atransmitting antenna, and said providing said distortion signalcomprises providing said output of said RF transmitter to said firstadaptive filter and said second adaptive filter.
 11. The process ofclaim 10, wherein: said filtering with said first adaptive filtercomprises varying a filtering characteristic of said first adaptivefilter in accordance with a result of said subtracting said output ofsaid first adaptive filter from said first one of said carrier signals,and said filtering with said second adaptive filter comprises varying afiltering characteristic of said second adaptive filter in accordancewith a result of said subtracting said output of said second adaptivefilter from said second one of said carrier signals.
 12. The process ofclaim 10 further comprising selecting as said model one of a pluralityof different versions of said model stored in an electronic memory insaid transceiver, wherein each of said different versions of said modelstored in said electronic memory corresponds to a different state ofsaid RF transceiver.
 13. A process of canceling transmit signal leakagedistortion from a received RF signal in an RF transceiver comprising anRF transmitter and an RF receiver, said process comprising: sensing acurrent state of said RF transceiver; selecting as a selected model oneof a plurality of different versions of a model of a transmission pathof said RF transmitter stored in an electronic memory, wherein each ofsaid different versions of said model corresponds to a different stateof said RF transceiver, wherein said selecting comprises selecting saidversion of said model stored in said electronic memory that correspondsto said current state of said RF transceiver; providing an RF signalfrom said RF transmitter as input to said selected one of said models toproduce a distortion signal; filtering said distortion signal with anadaptive filter; receiving a transmitted RF signal at said RFtransceiver subtracting an output of said adaptive filter from saidtransmitted RF signal received at said RF transceiver.
 14. The processof claim 13, wherein said receiving said transmitted RF signal at saidRF transceiver comprises: receiving a multicarrier RF signal comprisingcarrier signals each having a frequency within a different frequencypass-band; and separating said multicarrier RF signal into said carriersignals, wherein said RF signal is a first one of said carrier signals.15. The process of claim 14, wherein: said adaptive filter is a firstadaptive filter, said filtering comprises filtering with said firstadaptive filter said distortion signal, and said subtracting comprisessubtracting an output of said first adaptive filter from said first oneof said carrier signals; and wherein said process further comprises:filtering with a second adaptive filter said distortion signal, andsubtracting an output of said second adaptive filter from a second oneof said carrier signals.
 16. The process of 15, wherein: said filteringwith said first adaptive filter said distortion signal comprises varyinga filtering characteristic of said first adaptive filter in accordancewith a result of said subtracting an output of said first adaptivefilter from said first one of said carrier signals; and said filteringwith said second adaptive filter said distortion signal comprisesvarying a filtering characteristic of said second adaptive filter inaccordance with a result of said subtracting an output of said secondadaptive filter from said second one of said carrier signals.
 17. Theprocess of claim 16 further comprising: filtering with a third adaptivefilter said second one of said carrier signals; and subtracting anoutput of said third adaptive filter from said first one of said carriersignals.
 18. The process of claim 17, wherein: said filtering with saidthird adaptive filter comprises varying said third filteringcharacteristic of said third adaptive filter in accordance with: aresult of said subtracting said output of said third adaptive filterfrom said first one of said carrier signals, and said result of saidsubtracting said output of said first adaptive filter form said firstone of said carrier signals; and said filtering with said first adaptivefilter said distortion signal further comprises varying said firstfiltering characteristic in accordance with: said result of saidsubtracting said output of said third adaptive filter from said firstone of said carrier signals, and said result of said subtracting saidoutput of said first adaptive filter form said first one of said carriersignals.
 19. The process of claim 18 further comprising: filtering witha fourth adaptive filter said first one of said carrier signals; andsubtracting an output of said fourth adaptive filter from said secondone of said carrier signals.
 20. The process of claim 19, wherein: saidfiltering with said fourth adaptive filter comprises varying said fourthfiltering characteristic in accordance with: a result of saidsubtracting said output of said fourth adaptive filter from said secondone of said carrier signals, and said result of said subtracting saidoutput of said second adaptive filter form said second one of saidcarrier signals; and said filtering with said second adaptive filtersaid distortion signal further comprises varying said second filteringcharacteristic in accordance with: said result of said subtracting saidoutput of said fourth adaptive filter from said second one of saidcarrier signals, and said result of said subtracting said output of saidsecond adaptive filter form said second one of said carrier signals.